1. The Field of the Invention
The present invention relates generally to analysis of data transferred in a data transmission link.
2. The Relevant Technology
As the world becomes increasingly dependent on electronic data, there is an increased need for speed, bandwidth, and integrity in communication systems. Typically, various protocols are used to transfer data between the various components of a communication system. Examples of commonly used protocols are Fibre Channel, Gigabit Ethernet, Sonet, Infiniband, Rapid IO, PCI Xpress and others. Generally, the protocols are associated with a specific type of data communication. For example, the Fibre Channel protocol may be used to transfer data between storage area networks such as redundant array of inexpensive disk (RAID) systems, just a bunch of disks (JBOD) systems, workstations, and servers.
In these and other communication systems, testing for types of use, errors, and signal integrity can be advantageous. Often, problem identification, analysis, and resolution in communications systems involve capturing a portion of the network data traffic for review and analysis.
Various hardware and software tools have been developed to assist in analyzing data signals. In some cases, data capture is performed in connection with an optical transceiver that has a monitoring interface that is capable of performing diagnostic analysis of the network data. Such analysis is useful in monitoring parameters such as output power, input power, temperature, laser bias current, transceiver supply voltage, and the like.
Another tool that can be used to analyze integrity of signals transmitted over a data transmission link is an oscilloscope. One way that an oscilloscope can be used is to present an eye-diagram of an optical signal to a user. An eye-diagram can be used to analyze a signal for many purposes and can provide a visual representation of whether an interconnect meets an eye-diagram test specification for a given standard. Well known purposes for presenting an eye-diagram are to provide a measurement of total jitter (deterministic and random jitter combined) and extinction ratio (ratio of average high to average low logic level). Jitter can indicate how frequency is changing from bit to bit. Jitter can be represented in an eye-diagram by the vertical slope of the eye-diagram. Modern sampling oscilloscopes can display the jitter histogram at the threshold crossing and can use “eye masks” to spot violations of jitter and amplitude noise for both Fibre Channel and Gigabit Ethernet. An eye-diagram typically displays multiple waveform crossings simultaneously on an overlaid time base. Characterization of an eye-diagram can include mask testing as well as other eye-diagram measurements. While each of these tools provide useful information describing a data signal, traditional implementations of both oscillators and transceivers require a large amount of expensive equipment. Moreover, as data rates and bandwidth capabilities continue to increase, such equipment will become even more expensive. Thus, there is a need for a cost effective method and apparatus capable of generating both an eye diagram and digital diagnostics in a high speed data transmission link.